5 |
|
*/ |
6 |
|
|
7 |
|
package jsr166y; |
8 |
– |
|
8 |
|
import java.io.Serializable; |
9 |
|
import java.util.Collection; |
10 |
|
import java.util.List; |
42 |
|
* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
43 |
|
* The efficiency of {@code ForkJoinTask}s stems from a set of |
44 |
|
* restrictions (that are only partially statically enforceable) |
45 |
< |
* reflecting their intended use as computational tasks calculating |
46 |
< |
* pure functions or operating on purely isolated objects. The |
47 |
< |
* primary coordination mechanisms are {@link #fork}, that arranges |
45 |
> |
* reflecting their main use as computational tasks calculating pure |
46 |
> |
* functions or operating on purely isolated objects. The primary |
47 |
> |
* coordination mechanisms are {@link #fork}, that arranges |
48 |
|
* asynchronous execution, and {@link #join}, that doesn't proceed |
49 |
|
* until the task's result has been computed. Computations should |
50 |
< |
* avoid {@code synchronized} methods or blocks, and should minimize |
51 |
< |
* other blocking synchronization apart from joining other tasks or |
52 |
< |
* using synchronizers such as Phasers that are advertised to |
53 |
< |
* cooperate with fork/join scheduling. Tasks should also not perform |
54 |
< |
* blocking IO, and should ideally access variables that are |
55 |
< |
* completely independent of those accessed by other running |
56 |
< |
* tasks. Minor breaches of these restrictions, for example using |
57 |
< |
* shared output streams, may be tolerable in practice, but frequent |
58 |
< |
* use may result in poor performance, and the potential to |
59 |
< |
* indefinitely stall if the number of threads not waiting for IO or |
60 |
< |
* other external synchronization becomes exhausted. This usage |
61 |
< |
* restriction is in part enforced by not permitting checked |
62 |
< |
* exceptions such as {@code IOExceptions} to be thrown. However, |
63 |
< |
* computations may still encounter unchecked exceptions, that are |
64 |
< |
* rethrown to callers attempting to join them. These exceptions may |
65 |
< |
* additionally include {@link RejectedExecutionException} stemming |
66 |
< |
* from internal resource exhaustion, such as failure to allocate |
67 |
< |
* internal task queues. Rethrown exceptions behave in the same way as |
68 |
< |
* regular exceptions, but, when possible, contain stack traces (as |
69 |
< |
* displayed for example using {@code ex.printStackTrace()}) of both |
70 |
< |
* the thread that initiated the computation as well as the thread |
71 |
< |
* actually encountering the exception; minimally only the latter. |
50 |
> |
* ideally avoid {@code synchronized} methods or blocks, and should |
51 |
> |
* minimize other blocking synchronization apart from joining other |
52 |
> |
* tasks or using synchronizers such as Phasers that are advertised to |
53 |
> |
* cooperate with fork/join scheduling. Subdividable tasks should also |
54 |
> |
* not perform blocking IO, and should ideally access variables that |
55 |
> |
* are completely independent of those accessed by other running |
56 |
> |
* tasks. These guidelines are loosely enforced by not permitting |
57 |
> |
* checked exceptions such as {@code IOExceptions} to be |
58 |
> |
* thrown. However, computations may still encounter unchecked |
59 |
> |
* exceptions, that are rethrown to callers attempting to join |
60 |
> |
* them. These exceptions may additionally include {@link |
61 |
> |
* RejectedExecutionException} stemming from internal resource |
62 |
> |
* exhaustion, such as failure to allocate internal task |
63 |
> |
* queues. Rethrown exceptions behave in the same way as regular |
64 |
> |
* exceptions, but, when possible, contain stack traces (as displayed |
65 |
> |
* for example using {@code ex.printStackTrace()}) of both the thread |
66 |
> |
* that initiated the computation as well as the thread actually |
67 |
> |
* encountering the exception; minimally only the latter. |
68 |
> |
* |
69 |
> |
* <p>It is possible to define and use ForkJoinTasks that may block, |
70 |
> |
* but doing do requires three further considerations: (1) Completion |
71 |
> |
* of few if any <em>other</em> tasks should be dependent on a task |
72 |
> |
* that blocks on external synchronization or IO. Event-style async |
73 |
> |
* tasks that are never joined often fall into this category. (2) To |
74 |
> |
* minimize resource impact, tasks should be small; ideally performing |
75 |
> |
* only the (possibly) blocking action. (3) Unless the {@link |
76 |
> |
* ForkJoinPool.ManagedBlocker} API is used, or the number of possibly |
77 |
> |
* blocked tasks is known to be less than the pool's {@link |
78 |
> |
* ForkJoinPool#getParallelism} level, the pool cannot guarantee that |
79 |
> |
* enough threads will be available to ensure progress or good |
80 |
> |
* performance. |
81 |
|
* |
82 |
|
* <p>The primary method for awaiting completion and extracting |
83 |
|
* results of a task is {@link #join}, but there are several variants: |
93 |
|
* performs the most common form of parallel invocation: forking a set |
94 |
|
* of tasks and joining them all. |
95 |
|
* |
96 |
+ |
* <p>In the most typical usages, a fork-join pair act like a call |
97 |
+ |
* (fork) and return (join) from a parallel recursive function. As is |
98 |
+ |
* the case with other forms of recursive calls, returns (joins) |
99 |
+ |
* should be performed innermost-first. For example, {@code a.fork(); |
100 |
+ |
* b.fork(); b.join(); a.join();} is likely to be substantially more |
101 |
+ |
* efficient than joining {@code a} before {@code b}. |
102 |
+ |
* |
103 |
|
* <p>The execution status of tasks may be queried at several levels |
104 |
|
* of detail: {@link #isDone} is true if a task completed in any way |
105 |
|
* (including the case where a task was cancelled without executing); |
136 |
|
* supports other methods and techniques (for example the use of |
137 |
|
* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that |
138 |
|
* may be of use in constructing custom subclasses for problems that |
139 |
< |
* are not statically structured as DAGs. |
139 |
> |
* are not statically structured as DAGs. To support such usages a |
140 |
> |
* ForkJoinTask may be atomically <em>marked</em> using {@link |
141 |
> |
* #markForkJoinTask} and checked for marking using {@link |
142 |
> |
* #isMarkedForkJoinTask}. The ForkJoinTask implementation does not |
143 |
> |
* use these {@code protected} methods or marks for any purpose, but |
144 |
> |
* they may be of use in the construction of specialized subclasses. |
145 |
> |
* For example, parallel graph traversals can use the supplied methods |
146 |
> |
* to avoid revisiting nodes/tasks that have already been processed. |
147 |
> |
* Also, completion based designs can use them to record that one |
148 |
> |
* subtask has completed. (Method names for marking are bulky in part |
149 |
> |
* to encourage definition of methods that reflect their usage |
150 |
> |
* patterns.) |
151 |
|
* |
152 |
|
* <p>Most base support methods are {@code final}, to prevent |
153 |
|
* overriding of implementations that are intrinsically tied to the |
187 |
|
* See the internal documentation of class ForkJoinPool for a |
188 |
|
* general implementation overview. ForkJoinTasks are mainly |
189 |
|
* responsible for maintaining their "status" field amidst relays |
190 |
< |
* to methods in ForkJoinWorkerThread and ForkJoinPool. The |
191 |
< |
* methods of this class are more-or-less layered into (1) basic |
192 |
< |
* status maintenance (2) execution and awaiting completion (3) |
193 |
< |
* user-level methods that additionally report results. This is |
194 |
< |
* sometimes hard to see because this file orders exported methods |
195 |
< |
* in a way that flows well in javadocs. |
190 |
> |
* to methods in ForkJoinWorkerThread and ForkJoinPool. |
191 |
> |
* |
192 |
> |
* The methods of this class are more-or-less layered into |
193 |
> |
* (1) basic status maintenance |
194 |
> |
* (2) execution and awaiting completion |
195 |
> |
* (3) user-level methods that additionally report results. |
196 |
> |
* This is sometimes hard to see because this file orders exported |
197 |
> |
* methods in a way that flows well in javadocs. |
198 |
> |
*/ |
199 |
> |
|
200 |
> |
/** |
201 |
> |
* The number of times to try to help join a task without any |
202 |
> |
* apparent progress before giving up and blocking. The value is |
203 |
> |
* arbitrary but should be large enough to cope with transient |
204 |
> |
* stalls (due to GC etc) that can cause helping methods not to be |
205 |
> |
* able to proceed because other workers have not progressed to |
206 |
> |
* the point where subtasks can be found or taken. |
207 |
|
*/ |
208 |
+ |
private static final int HELP_RETRIES = 32; |
209 |
|
|
210 |
|
/* |
211 |
|
* The status field holds run control status bits packed into a |
226 |
|
|
227 |
|
/** The run status of this task */ |
228 |
|
volatile int status; // accessed directly by pool and workers |
229 |
< |
private static final int NORMAL = -1; |
230 |
< |
private static final int CANCELLED = -2; |
231 |
< |
private static final int EXCEPTIONAL = -3; |
232 |
< |
private static final int SIGNAL = 1; |
229 |
> |
static final int NORMAL = 0xfffffffc; // negative with low 2 bits 0 |
230 |
> |
static final int CANCELLED = 0xfffffff8; // must be < NORMAL |
231 |
> |
static final int EXCEPTIONAL = 0xfffffff4; // must be < CANCELLED |
232 |
> |
static final int SIGNAL = 0x00000001; |
233 |
> |
static final int MARKED = 0x00000002; |
234 |
|
|
235 |
|
/** |
236 |
< |
* Marks completion and wakes up threads waiting to join this task, |
237 |
< |
* also clearing signal request bits. |
236 |
> |
* Marks completion and wakes up threads waiting to join this |
237 |
> |
* task, also clearing signal request bits. A specialization for |
238 |
> |
* NORMAL completion is in method doExec. |
239 |
|
* |
240 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
241 |
|
* @return completion status on exit |
244 |
|
for (int s;;) { |
245 |
|
if ((s = status) < 0) |
246 |
|
return s; |
247 |
< |
if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) { |
248 |
< |
if (s != 0) |
247 |
> |
if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|completion)) { |
248 |
> |
if ((s & SIGNAL) != 0) |
249 |
|
synchronized (this) { notifyAll(); } |
250 |
|
return completion; |
251 |
|
} |
253 |
|
} |
254 |
|
|
255 |
|
/** |
256 |
< |
* Tries to block a worker thread until completed or timed out. |
257 |
< |
* Uses Object.wait time argument conventions. |
258 |
< |
* May fail on contention or interrupt. |
256 |
> |
* Primary execution method for stolen tasks. Unless done, calls |
257 |
> |
* exec and records status if completed, but doesn't wait for |
258 |
> |
* completion otherwise. |
259 |
|
* |
260 |
< |
* @param millis if > 0, wait time. |
260 |
> |
* @return status on exit from this method |
261 |
|
*/ |
262 |
< |
final void tryAwaitDone(long millis) { |
263 |
< |
int s; |
264 |
< |
try { |
265 |
< |
if (((s = status) > 0 || |
266 |
< |
(s == 0 && |
267 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, 0, SIGNAL))) && |
268 |
< |
status > 0) { |
269 |
< |
synchronized (this) { |
270 |
< |
if (status > 0) |
271 |
< |
wait(millis); |
262 |
> |
final int doExec() { |
263 |
> |
int s; boolean completed; |
264 |
> |
if ((s = status) >= 0) { |
265 |
> |
try { |
266 |
> |
completed = exec(); |
267 |
> |
} catch (Throwable rex) { |
268 |
> |
return setExceptionalCompletion(rex); |
269 |
> |
} |
270 |
> |
while ((s = status) >= 0 && completed) { |
271 |
> |
if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|NORMAL)) { |
272 |
> |
if ((s & SIGNAL) != 0) |
273 |
> |
synchronized (this) { notifyAll(); } |
274 |
> |
return NORMAL; |
275 |
|
} |
276 |
|
} |
234 |
– |
} catch (InterruptedException ie) { |
235 |
– |
// caller must check termination |
277 |
|
} |
278 |
+ |
return s; |
279 |
|
} |
280 |
|
|
281 |
|
/** |
288 |
|
boolean interrupted = false; |
289 |
|
synchronized (this) { |
290 |
|
while ((s = status) >= 0) { |
291 |
< |
if (s == 0) |
250 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, |
251 |
< |
0, SIGNAL); |
252 |
< |
else { |
291 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
292 |
|
try { |
293 |
|
wait(); |
294 |
|
} catch (InterruptedException ie) { |
314 |
|
if ((s = status) >= 0) { |
315 |
|
synchronized (this) { |
316 |
|
while ((s = status) >= 0) { |
317 |
< |
if (s == 0) |
279 |
< |
UNSAFE.compareAndSwapInt(this, statusOffset, |
280 |
< |
0, SIGNAL); |
281 |
< |
else { |
317 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
318 |
|
wait(millis); |
319 |
|
if (millis > 0L) |
320 |
|
break; |
325 |
|
return s; |
326 |
|
} |
327 |
|
|
328 |
+ |
|
329 |
|
/** |
330 |
< |
* Primary execution method for stolen tasks. Unless done, calls |
331 |
< |
* exec and records status if completed, but doesn't wait for |
332 |
< |
* completion otherwise. |
330 |
> |
* Implementation for join, get, quietlyJoin. Directly handles |
331 |
> |
* only cases of already-completed, external wait, and |
332 |
> |
* unfork+exec. Others are relayed to awaitJoin. |
333 |
> |
* |
334 |
> |
* @return status upon completion |
335 |
|
*/ |
336 |
< |
final void doExec() { |
337 |
< |
if (status >= 0) { |
338 |
< |
boolean completed; |
339 |
< |
try { |
340 |
< |
completed = exec(); |
341 |
< |
} catch (Throwable rex) { |
342 |
< |
setExceptionalCompletion(rex); |
343 |
< |
return; |
305 |
< |
} |
306 |
< |
if (completed) |
307 |
< |
setCompletion(NORMAL); // must be outside try block |
336 |
> |
private int doJoin() { |
337 |
> |
int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w; |
338 |
> |
if ((s = status) >= 0) { |
339 |
> |
if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) |
340 |
> |
s = externalAwaitDone(); |
341 |
> |
else if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue). |
342 |
> |
tryUnpush(this) || (s = doExec()) >= 0) |
343 |
> |
s = awaitJoin(w, wt.pool); |
344 |
|
} |
345 |
+ |
return s; |
346 |
|
} |
347 |
|
|
348 |
|
/** |
349 |
< |
* Primary mechanics for join, get, quietlyJoin. |
349 |
> |
* Helps and/or blocks until joined. |
350 |
> |
* |
351 |
> |
* @param w the joiner |
352 |
> |
* @param p the pool |
353 |
|
* @return status upon completion |
354 |
|
*/ |
355 |
< |
private int doJoin() { |
356 |
< |
Thread t; ForkJoinWorkerThread w; int s; boolean completed; |
357 |
< |
if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) { |
358 |
< |
if ((s = status) < 0) |
359 |
< |
return s; |
360 |
< |
if ((w = (ForkJoinWorkerThread)t).unpushTask(this)) { |
355 |
> |
private int awaitJoin(ForkJoinPool.WorkQueue w, ForkJoinPool p) { |
356 |
> |
int s; |
357 |
> |
ForkJoinTask<?> prevJoin = w.currentJoin; |
358 |
> |
w.currentJoin = this; |
359 |
> |
for (int k = HELP_RETRIES; (s = status) >= 0;) { |
360 |
> |
if ((w.queueSize() > 0) ? |
361 |
> |
w.tryRemoveAndExec(this) : // self-help |
362 |
> |
p.tryHelpStealer(w, this)) // help process tasks |
363 |
> |
k = HELP_RETRIES; // reset if made progress |
364 |
> |
else if ((s = status) < 0) // recheck |
365 |
> |
break; |
366 |
> |
else if (--k > 0) { |
367 |
> |
if ((k & 3) == 1) |
368 |
> |
Thread.yield(); // occasionally yield |
369 |
> |
} |
370 |
> |
else if (k == 0) |
371 |
> |
p.tryPollForAndExec(w, this); // uncommon self-help case |
372 |
> |
else if (p.tryCompensate()) { // true if can block |
373 |
|
try { |
374 |
< |
completed = exec(); |
375 |
< |
} catch (Throwable rex) { |
376 |
< |
return setExceptionalCompletion(rex); |
374 |
> |
int ss = status; |
375 |
> |
if (ss >= 0 && // assert need signal |
376 |
> |
U.compareAndSwapInt(this, STATUS, ss, ss | SIGNAL)) { |
377 |
> |
synchronized (this) { |
378 |
> |
if (status >= 0) // block |
379 |
> |
wait(); |
380 |
> |
} |
381 |
> |
} |
382 |
> |
} catch (InterruptedException ignore) { |
383 |
> |
} finally { |
384 |
> |
p.incrementActiveCount(); // re-activate |
385 |
|
} |
326 |
– |
if (completed) |
327 |
– |
return setCompletion(NORMAL); |
386 |
|
} |
329 |
– |
return w.joinTask(this); |
387 |
|
} |
388 |
< |
else |
389 |
< |
return externalAwaitDone(); |
388 |
> |
w.currentJoin = prevJoin; |
389 |
> |
return s; |
390 |
|
} |
391 |
|
|
392 |
|
/** |
393 |
< |
* Primary mechanics for invoke, quietlyInvoke. |
393 |
> |
* Implementation for invoke, quietlyInvoke. |
394 |
> |
* |
395 |
|
* @return status upon completion |
396 |
|
*/ |
397 |
|
private int doInvoke() { |
398 |
< |
int s; boolean completed; |
399 |
< |
if ((s = status) < 0) |
400 |
< |
return s; |
401 |
< |
try { |
402 |
< |
completed = exec(); |
403 |
< |
} catch (Throwable rex) { |
404 |
< |
return setExceptionalCompletion(rex); |
398 |
> |
int s; Thread t; |
399 |
> |
if ((s = doExec()) >= 0) { |
400 |
> |
if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) |
401 |
> |
s = externalAwaitDone(); |
402 |
> |
else { |
403 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
404 |
> |
s = awaitJoin(wt.workQueue, wt.pool); |
405 |
> |
} |
406 |
|
} |
407 |
< |
if (completed) |
349 |
< |
return setCompletion(NORMAL); |
350 |
< |
else |
351 |
< |
return doJoin(); |
407 |
> |
return s; |
408 |
|
} |
409 |
|
|
410 |
|
// Exception table support |
479 |
|
} |
480 |
|
|
481 |
|
/** |
482 |
+ |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
483 |
+ |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
484 |
+ |
* exceptions, but if it does anyway, we have no recourse during |
485 |
+ |
* shutdown, so guard against this case. |
486 |
+ |
*/ |
487 |
+ |
static final void cancelIgnoringExceptions(ForkJoinTask<?> t) { |
488 |
+ |
if (t != null && t.status >= 0) { |
489 |
+ |
try { |
490 |
+ |
t.cancel(false); |
491 |
+ |
} catch (Throwable ignore) { |
492 |
+ |
} |
493 |
+ |
} |
494 |
+ |
} |
495 |
+ |
|
496 |
+ |
/** |
497 |
|
* Removes exception node and clears status |
498 |
|
*/ |
499 |
|
private void clearExceptionalCompletion() { |
632 |
|
if ((s = status) == CANCELLED) |
633 |
|
throw new CancellationException(); |
634 |
|
if (s == EXCEPTIONAL && (ex = getThrowableException()) != null) |
635 |
< |
UNSAFE.throwException(ex); |
635 |
> |
U.throwException(ex); |
636 |
|
return getRawResult(); |
637 |
|
} |
638 |
|
|
657 |
|
* @return {@code this}, to simplify usage |
658 |
|
*/ |
659 |
|
public final ForkJoinTask<V> fork() { |
660 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
661 |
< |
.pushTask(this); |
660 |
> |
ForkJoinWorkerThread wt; |
661 |
> |
(wt = (ForkJoinWorkerThread)Thread.currentThread()). |
662 |
> |
workQueue.push(this, wt.pool); |
663 |
|
return this; |
664 |
|
} |
665 |
|
|
765 |
|
if (t != null) { |
766 |
|
if (ex != null) |
767 |
|
t.cancel(false); |
768 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
768 |
> |
else if (t.doJoin() < NORMAL) |
769 |
|
ex = t.getException(); |
770 |
|
} |
771 |
|
} |
772 |
|
if (ex != null) |
773 |
< |
UNSAFE.throwException(ex); |
773 |
> |
U.throwException(ex); |
774 |
|
} |
775 |
|
|
776 |
|
/** |
822 |
|
if (t != null) { |
823 |
|
if (ex != null) |
824 |
|
t.cancel(false); |
825 |
< |
else if (t.doJoin() < NORMAL && ex == null) |
825 |
> |
else if (t.doJoin() < NORMAL) |
826 |
|
ex = t.getException(); |
827 |
|
} |
828 |
|
} |
829 |
|
if (ex != null) |
830 |
< |
UNSAFE.throwException(ex); |
830 |
> |
U.throwException(ex); |
831 |
|
return tasks; |
832 |
|
} |
833 |
|
|
862 |
|
return setCompletion(CANCELLED) == CANCELLED; |
863 |
|
} |
864 |
|
|
793 |
– |
/** |
794 |
– |
* Cancels, ignoring any exceptions thrown by cancel. Used during |
795 |
– |
* worker and pool shutdown. Cancel is spec'ed not to throw any |
796 |
– |
* exceptions, but if it does anyway, we have no recourse during |
797 |
– |
* shutdown, so guard against this case. |
798 |
– |
*/ |
799 |
– |
final void cancelIgnoringExceptions() { |
800 |
– |
try { |
801 |
– |
cancel(false); |
802 |
– |
} catch (Throwable ignore) { |
803 |
– |
} |
804 |
– |
} |
805 |
– |
|
865 |
|
public final boolean isDone() { |
866 |
|
return status < 0; |
867 |
|
} |
985 |
|
*/ |
986 |
|
public final V get(long timeout, TimeUnit unit) |
987 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
988 |
+ |
// Messy in part because we measure in nanos, but wait in millis |
989 |
+ |
int s; long millis, nanos; |
990 |
|
Thread t = Thread.currentThread(); |
991 |
< |
if (t instanceof ForkJoinWorkerThread) { |
992 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
993 |
< |
long nanos = unit.toNanos(timeout); |
994 |
< |
if (status >= 0) { |
995 |
< |
boolean completed = false; |
996 |
< |
if (w.unpushTask(this)) { |
997 |
< |
try { |
998 |
< |
completed = exec(); |
999 |
< |
} catch (Throwable rex) { |
1000 |
< |
setExceptionalCompletion(rex); |
991 |
> |
if (!(t instanceof ForkJoinWorkerThread)) { |
992 |
> |
if ((millis = unit.toMillis(timeout)) > 0L) |
993 |
> |
s = externalInterruptibleAwaitDone(millis); |
994 |
> |
else |
995 |
> |
s = status; |
996 |
> |
} |
997 |
> |
else if ((s = status) >= 0 && (nanos = unit.toNanos(timeout)) > 0L) { |
998 |
> |
long deadline = System.nanoTime() + nanos; |
999 |
> |
ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t; |
1000 |
> |
ForkJoinPool.WorkQueue w = wt.workQueue; |
1001 |
> |
ForkJoinPool p = wt.pool; |
1002 |
> |
if (w.tryUnpush(this)) |
1003 |
> |
doExec(); |
1004 |
> |
boolean blocking = false; |
1005 |
> |
try { |
1006 |
> |
while ((s = status) >= 0) { |
1007 |
> |
if (w.runState < 0) |
1008 |
> |
cancelIgnoringExceptions(this); |
1009 |
> |
else if (!blocking) |
1010 |
> |
blocking = p.tryCompensate(); |
1011 |
> |
else { |
1012 |
> |
millis = TimeUnit.NANOSECONDS.toMillis(nanos); |
1013 |
> |
if (millis > 0L && |
1014 |
> |
U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) { |
1015 |
> |
try { |
1016 |
> |
synchronized (this) { |
1017 |
> |
if (status >= 0) |
1018 |
> |
wait(millis); |
1019 |
> |
} |
1020 |
> |
} catch (InterruptedException ie) { |
1021 |
> |
} |
1022 |
> |
} |
1023 |
> |
if ((s = status) < 0 || |
1024 |
> |
(nanos = deadline - System.nanoTime()) <= 0L) |
1025 |
> |
break; |
1026 |
|
} |
1027 |
|
} |
1028 |
< |
if (completed) |
1029 |
< |
setCompletion(NORMAL); |
1030 |
< |
else if (status >= 0 && nanos > 0) |
945 |
< |
w.pool.timedAwaitJoin(this, nanos); |
1028 |
> |
} finally { |
1029 |
> |
if (blocking) |
1030 |
> |
p.incrementActiveCount(); |
1031 |
|
} |
1032 |
|
} |
948 |
– |
else { |
949 |
– |
long millis = unit.toMillis(timeout); |
950 |
– |
if (millis > 0) |
951 |
– |
externalInterruptibleAwaitDone(millis); |
952 |
– |
} |
953 |
– |
int s = status; |
1033 |
|
if (s != NORMAL) { |
1034 |
|
Throwable ex; |
1035 |
|
if (s == CANCELLED) |
1075 |
|
* ClassCastException}. |
1076 |
|
*/ |
1077 |
|
public static void helpQuiesce() { |
1078 |
< |
((ForkJoinWorkerThread) Thread.currentThread()) |
1079 |
< |
.helpQuiescePool(); |
1078 |
> |
ForkJoinWorkerThread wt = |
1079 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1080 |
> |
wt.pool.helpQuiescePool(wt.workQueue); |
1081 |
|
} |
1082 |
|
|
1083 |
|
/** |
1145 |
|
* @return {@code true} if unforked |
1146 |
|
*/ |
1147 |
|
public boolean tryUnfork() { |
1148 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1149 |
< |
.unpushTask(this); |
1148 |
> |
return ((ForkJoinWorkerThread)Thread.currentThread()) |
1149 |
> |
.workQueue.tryUnpush(this); |
1150 |
|
} |
1151 |
|
|
1152 |
|
/** |
1165 |
|
*/ |
1166 |
|
public static int getQueuedTaskCount() { |
1167 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1168 |
< |
.getQueueSize(); |
1168 |
> |
.workQueue.queueSize(); |
1169 |
|
} |
1170 |
|
|
1171 |
|
/** |
1187 |
|
* @return the surplus number of tasks, which may be negative |
1188 |
|
*/ |
1189 |
|
public static int getSurplusQueuedTaskCount() { |
1190 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1191 |
< |
.getEstimatedSurplusTaskCount(); |
1190 |
> |
/* |
1191 |
> |
* The aim of this method is to return a cheap heuristic guide |
1192 |
> |
* for task partitioning when programmers, frameworks, tools, |
1193 |
> |
* or languages have little or no idea about task granularity. |
1194 |
> |
* In essence by offering this method, we ask users only about |
1195 |
> |
* tradeoffs in overhead vs expected throughput and its |
1196 |
> |
* variance, rather than how finely to partition tasks. |
1197 |
> |
* |
1198 |
> |
* In a steady state strict (tree-structured) computation, |
1199 |
> |
* each thread makes available for stealing enough tasks for |
1200 |
> |
* other threads to remain active. Inductively, if all threads |
1201 |
> |
* play by the same rules, each thread should make available |
1202 |
> |
* only a constant number of tasks. |
1203 |
> |
* |
1204 |
> |
* The minimum useful constant is just 1. But using a value of |
1205 |
> |
* 1 would require immediate replenishment upon each steal to |
1206 |
> |
* maintain enough tasks, which is infeasible. Further, |
1207 |
> |
* partitionings/granularities of offered tasks should |
1208 |
> |
* minimize steal rates, which in general means that threads |
1209 |
> |
* nearer the top of computation tree should generate more |
1210 |
> |
* than those nearer the bottom. In perfect steady state, each |
1211 |
> |
* thread is at approximately the same level of computation |
1212 |
> |
* tree. However, producing extra tasks amortizes the |
1213 |
> |
* uncertainty of progress and diffusion assumptions. |
1214 |
> |
* |
1215 |
> |
* So, users will want to use values larger, but not much |
1216 |
> |
* larger than 1 to both smooth over transient shortages and |
1217 |
> |
* hedge against uneven progress; as traded off against the |
1218 |
> |
* cost of extra task overhead. We leave the user to pick a |
1219 |
> |
* threshold value to compare with the results of this call to |
1220 |
> |
* guide decisions, but recommend values such as 3. |
1221 |
> |
* |
1222 |
> |
* When all threads are active, it is on average OK to |
1223 |
> |
* estimate surplus strictly locally. In steady-state, if one |
1224 |
> |
* thread is maintaining say 2 surplus tasks, then so are |
1225 |
> |
* others. So we can just use estimated queue length. |
1226 |
> |
* However, this strategy alone leads to serious mis-estimates |
1227 |
> |
* in some non-steady-state conditions (ramp-up, ramp-down, |
1228 |
> |
* other stalls). We can detect many of these by further |
1229 |
> |
* considering the number of "idle" threads, that are known to |
1230 |
> |
* have zero queued tasks, so compensate by a factor of |
1231 |
> |
* (#idle/#active) threads. |
1232 |
> |
*/ |
1233 |
> |
ForkJoinWorkerThread wt = |
1234 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1235 |
> |
return wt.workQueue.queueSize() - wt.pool.idlePerActive(); |
1236 |
|
} |
1237 |
|
|
1238 |
|
// Extension methods |
1289 |
|
* @return the next task, or {@code null} if none are available |
1290 |
|
*/ |
1291 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1292 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1169 |
< |
.peekTask(); |
1292 |
> |
return ((ForkJoinWorkerThread) Thread.currentThread()).workQueue.peek(); |
1293 |
|
} |
1294 |
|
|
1295 |
|
/** |
1308 |
|
*/ |
1309 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1310 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1311 |
< |
.pollLocalTask(); |
1311 |
> |
.workQueue.nextLocalTask(); |
1312 |
|
} |
1313 |
|
|
1314 |
|
/** |
1330 |
|
* @return a task, or {@code null} if none are available |
1331 |
|
*/ |
1332 |
|
protected static ForkJoinTask<?> pollTask() { |
1333 |
< |
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1334 |
< |
.pollTask(); |
1333 |
> |
ForkJoinWorkerThread wt = |
1334 |
> |
(ForkJoinWorkerThread)Thread.currentThread(); |
1335 |
> |
return wt.pool.nextTaskFor(wt.workQueue); |
1336 |
> |
} |
1337 |
> |
|
1338 |
> |
// Mark-bit operations |
1339 |
> |
|
1340 |
> |
/** |
1341 |
> |
* Returns true if this task is marked. |
1342 |
> |
* |
1343 |
> |
* @return true if this task is marked |
1344 |
> |
* @since 1.8 |
1345 |
> |
*/ |
1346 |
> |
public final boolean isMarkedForkJoinTask() { |
1347 |
> |
return (status & MARKED) != 0; |
1348 |
> |
} |
1349 |
> |
|
1350 |
> |
/** |
1351 |
> |
* Atomically sets the mark on this task. |
1352 |
> |
* |
1353 |
> |
* @return true if this task was previously unmarked |
1354 |
> |
* @since 1.8 |
1355 |
> |
*/ |
1356 |
> |
public final boolean markForkJoinTask() { |
1357 |
> |
for (int s;;) { |
1358 |
> |
if (((s = status) & MARKED) != 0) |
1359 |
> |
return false; |
1360 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s | MARKED)) |
1361 |
> |
return true; |
1362 |
> |
} |
1363 |
> |
} |
1364 |
> |
|
1365 |
> |
/** |
1366 |
> |
* Atomically clears the mark on this task. |
1367 |
> |
* |
1368 |
> |
* @return true if this task was previously marked |
1369 |
> |
* @since 1.8 |
1370 |
> |
*/ |
1371 |
> |
public final boolean unmarkForkJoinTask() { |
1372 |
> |
for (int s;;) { |
1373 |
> |
if (((s = status) & MARKED) == 0) |
1374 |
> |
return false; |
1375 |
> |
if (U.compareAndSwapInt(this, STATUS, s, s & ~MARKED)) |
1376 |
> |
return true; |
1377 |
> |
} |
1378 |
|
} |
1379 |
|
|
1380 |
|
/** |
1475 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1476 |
|
|
1477 |
|
/** |
1478 |
< |
* Saves the state to a stream (that is, serializes it). |
1478 |
> |
* Saves this task to a stream (that is, serializes it). |
1479 |
|
* |
1480 |
|
* @serialData the current run status and the exception thrown |
1481 |
|
* during execution, or {@code null} if none |
1316 |
– |
* @param s the stream |
1482 |
|
*/ |
1483 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1484 |
|
throws java.io.IOException { |
1487 |
|
} |
1488 |
|
|
1489 |
|
/** |
1490 |
< |
* Reconstitutes the instance from a stream (that is, deserializes it). |
1326 |
< |
* |
1327 |
< |
* @param s the stream |
1490 |
> |
* Reconstitutes this task from a stream (that is, deserializes it). |
1491 |
|
*/ |
1492 |
|
private void readObject(java.io.ObjectInputStream s) |
1493 |
|
throws java.io.IOException, ClassNotFoundException { |
1498 |
|
} |
1499 |
|
|
1500 |
|
// Unsafe mechanics |
1501 |
< |
private static final sun.misc.Unsafe UNSAFE; |
1502 |
< |
private static final long statusOffset; |
1501 |
> |
private static final sun.misc.Unsafe U; |
1502 |
> |
private static final long STATUS; |
1503 |
|
static { |
1504 |
|
exceptionTableLock = new ReentrantLock(); |
1505 |
|
exceptionTableRefQueue = new ReferenceQueue<Object>(); |
1506 |
|
exceptionTable = new ExceptionNode[EXCEPTION_MAP_CAPACITY]; |
1507 |
|
try { |
1508 |
< |
UNSAFE = getUnsafe(); |
1509 |
< |
statusOffset = UNSAFE.objectFieldOffset |
1508 |
> |
U = getUnsafe(); |
1509 |
> |
STATUS = U.objectFieldOffset |
1510 |
|
(ForkJoinTask.class.getDeclaredField("status")); |
1511 |
|
} catch (Exception e) { |
1512 |
|
throw new Error(e); |